In the latest style of building, for the purpose of increasing efficiency of utilization of construction materials and efficiently utilizing the space in the room by making the ceiling as low as possible, there is a tendency to use a flash type sprinkler head which has fewer portions left open to view on the ceiling board. Since this flash type sprinkler head contains a setting portion having a smaller diameter than that of the head-setting hole provided on the ceiling board, it is advantageously possible to set the sprinkler head onto the sprinkler piping before boarding the ceiling, and therefore this type of sprinkler head has a great advantage, which does not exist in the other type of sprinkler head, that the work of mounting or setting the same to the sprinkler piping in each room in the building can be effected before and without being influenced by the process of boarding the ceiling.
As the conventional flash type sprinkler heads, there are shown some examples in Japanese Utility Model Publication (examined) Nos. 8239/1978 and 49636/1981 and Japanese Utility Model Publication (unexamined) No. 97565/1982, which are shown in FIGS. 1, 2 and 3 of the accompanying drawing, respectively.
An explanation is now made of the fundamental construction and operation of a conventional flash type sprinkler head with reference to FIG. 1. In FIG. 1, the sprinkler head comprises a main body 1, a valve member 7 which is installed on the tip opening portion of the main body 1, i.e., a drain opening portion, and a heat sensitive detachable member 15 which can sense the heat of flames to disassemble and scatter. The main body 1, which has a downwardly decreasing internal diameter, mainly comprises a connecting pipe portion and a straight pipe portion at the upper and lower halves thereof. The connecting pipe portion is provided, on its outer side, with male screw threads which connects to the sprinkler piping, and the straight pipe portion, has a drain opening portion on its lower end. On the outer periphery of the upper end of the straight pipe portion, there is formed a flange having a male screw member 1' for connection to a cylindrical frame 2 to screw-fix the cylindrical frame 2 to the main body with the cylindrical frame 2 to the main body with the cyldrical frame hanging downward. On the outside of the straight pipe portion there is fixed a deflector ring 6, and a deflector 5 of the drain opening is connected through the connecting leg of the deflector ring 6. The portion of the deflector 5 provided on the lower portion of the drain opening contains the valve member 7 which closes the end surface of the drain opening and is held by the heat sensitive detachable member on the lower end of the frame.
The valve member 7 which comprises a gasket 3 made of copper packing, etc. and a valve cap 4 covered with the gasket is installed on the valve seat on the tip end of the drain opening. On the setting-up of the sprinkler head the tightening force of the frame 2 onto the flange is converted into a pressing force by which the valve cap 4 closes the end surface of the drain opening.
The heat sensitive detachable member 15 contains a pair of levers 10 which are hooked on an inwardly directed flange on the lower end of the frame 2, a setting plate 11 which is positioned on the upper portion of the levers and supported by the levers 10 which are inserted therethrough, a balancer 12 which is positioned at the lower portion of the levers 10, a heat sensitive cylinder 13 which is inserted through the setting plate 11 and held with the balancer 12, a heat sensitive (heat conductive) piston 14, a heat sensitive (heat conductive) plate 16 which contains said heat sensitive cylinder 13 and the heat sensitive piston 14 and is provided hanging on the lower end of the frame 2, and a fusible segment 17 formed of a material which melts when exposed to the heat of a fire, which is held between the heat sensitive cylinder 13 held to the balancer 12 against the tightening force of the frame 2 and the heat sensitive piston 14 screwed to the setting plate 11.
As soon as the heat sensitive plate 16, the heat sensitive cylinder 13 and the heat sensitive piston 14 sense the heat generated by fire and the fusible segment made of an alloy having low melting point is melted, the balance of the tightening force between the heat sensitive piston 14 and the heat sensitive cylinder 13 which support the fusible segment 17 and the frame 2 is broken, whereby the heat sensitive piston 14, the heat sensitive cylinder 13 and the heat sensitive plate 16 are pushed upward by the levers 10 and the balancer 12. Then the levers 10 are rotated outward so as to disconnect both ends of the balancer 12 from the jointing hole portion of the levers 10, and thereby the setting plate 11 is also free from the levers 10. Thus, each element of the heat sensitive detachable member 15 falls down while disassembling and scattering. Accordingly, the valve member 7, the deflector 5 and the deflector ring 6, which are out of the supporting elements at the lower end, move downward inside the frame 2, and the deflector ring 6 is then set on the inwardly directed flange at the lower opening portion of the frame 2 so as to support the deflector 5 in a hanging disposition. As a result, the pressurized water in the sprinkler piping spouts out from the drain opening from which the valve member 7 is removed and dashes against the deflector 5, whereby the water scatters in all directions so as to extinguish the fire. This process from the sensing of heat to the drainage is almost instantaneously effected.
In the conventional sprinkler head having a construction as described above, the transmission of heat to the fusible segment from the other heat sensitive elements in the heat sensitive detachable member can afford the sprinkler head to sense the fire, and the fusible segment is melted to release the drain opening of the tip end of the sprinkler piping so as to scatter the pressurized water. In the thus constructed sprinkler head, however, as shown in FIGS. 1 and 2, since the heat sensitive plate 16 has no perforations on its lower surface, peripheral wall or connecting portion, it is impossible to observe the condition of the fusible segment 17, which is completely surrounded with the heat sensitive plate 16, without removing the heat sensitive plate 16. Accordingly, changing conditions of the fusible segment or the surroundings of the same with the lapse of time cannot be observed. Another disadvantage is as follows: since the fusible segment of said sprinkler head is compressed by the tightening and pressing force of the heat sensitive cylinder 13 and the heat sensitive piston 14 which are supported by the levers 10 and the balancer 12, while maintaining the balance [12, while maintaining the balance] with the tightening force of the frame 2 against the flange 1' of the main body, the sizes of the detachable member and the heat sensitive member is necessarily long in the vertical direction. Thus, there is a need for a smaller sprinkler.